Two major studies to be conducted will attempt to establish the relationship between CNS serotonergic activity and measures of impulsivity and aggression among two groups of male and female parolees. These parolees will be divided into 2 groups based upon a history of violence or non-violence. Laboratory measures of aggressive responding and impulsivity will be determined. Studies conducted at the CRC will assess serotonergic activity by measuring the prolactin response to a buspirone challenge. The studies conducted at the CRC have been completed. Male and female parolees participated in neuroendocrine challenge studies to assess serotonin activity using buspirone challenge. A second study with patients with past drug dependence and matched controls has also been completed. This study used ipsapirone as a challenge agent.